1. Technical Field of the Invention
The present invention relates to sectorized antenna for use with cellular communication systems, and more particularly, to a sectorized antenna configuration utilizing a plurality of frequencies having their beamwidth focused within a plurality of equally spaced sectors about a base station site.
2. Description of Related Art
Personal Communication Services (PCS) Systems provide users with a variety of wireless telephone services through low-power portable telephone units. The popularity of PCS is expected to grow exponentially over the next few years and PCS operators in the U.S. are faced with the problem of providing nationwide coverage to attract subscribers. The use of large cells is required in order for providers to economically provide nationwide coverage to their subscribers.
However, PCS phones need to be smaller and have longer talk times. This requires lower power consumption by the telephone unit. In order to maintain presently existing or larger cell sizes in conjunction with units having lower power output requires improvement of base station receiving capabilities. With noise factors perhaps already as low as possible, one solution for obtaining better base station receiver capabilities may be by reducing cabling loses with active antennas. Improved antenna arrangement and the use of more diversity reception are additional solutions for improving the receiver characteristics of the base station.
The foregoing and other problems are overcome by the method and apparatus of the present invention for improving the receiver characteristics of a base station. A normal three-sector base station site having a plurality of assigned channel frequencies is subdivided into a plurality of 120xc2x0 sectors wherein each of the sectors has a sector antenna generating a directional antenna beam for the sector.
A plurality of channel frequencies are assigned to each of the sectors such that the base station transmits and receives along each sector antenna only the assigned frequencies for the sector. For a cellular telephone system such as DAMPS, the frequency channels are equally divided among each of the sectors such that no particular frequency is used within more than one sector. However, in a GSM type system, frequencies within a particular sector may be shared with adjacent sectors via frequency hopping techniques.
By increasing the number of sectors around a particular base station and uniquely assigning a group of channel frequencies to each sector, the likelihood of a portable mobile unit residing within a beam peak is greatly increased. Furthermore, the angular distance from a beam peak, and thus the gain losses, are necessarily smaller. These factor combine to improve the receiver characteristics of the base station for lower power telephone units. The system may further improve receiver characteristics using diversity combinations between signals received in adjacent sectors from the same telephone unit.